Photographic film



Sept. l5, 1936. W FORSTM ANN 2,054,284

PHOTOGRAPHIC FILM Filed May 3l, 1933 @ferme/hl? layer canta/'mkg f//e ame f/,ae of fella/05e ester z5 f//e f//m odf VIH y f a 'cnu' 'Patented Sept. 15, 1936 PATENT OFFICE PHOTOGRAPHIC FILM Walther Forstmann,

Berlin- Schoneberg,

Ger-

many, assigner to Voigtlander & Sohn Aktiengesellschaft, Brunswick, Germany Application May 31, 1933, serial Nol 673,5995/2 In Germany June 6, 1932 5 Claims. (Cl. 95-9) My invention relates to photographic lms, more especially of the kind in which an intermediate substratum layer is inserted between the sensitive layer and the lm body serving as carrier of this sensitive layer.

It is an object of my invention to provide a film comprising such an intermediate layer which is superior to similar layers hitherto used as far as the power to hold the sensitive layer on the carrier is concerned.

As is well known to those skilled in the art, a. gelatine layer as constituted by a photographic emulsion, when arranged directly on a base or carrier such as cellulose nitrate, cellulose acetate or the like, will not adhere to this carrier as solidly as required in practical use. After the gelatine has dried down on the carrier, it can as a rule be stripped as a whole, and on being acted upon by a watery liquid, such las a developer, xation or reinforcing liquor, the gelatine layer will frequently come oif, starting from the edges.

In order to improve the adhesion of the sensitive layer to the carrier or film body an intermediate layer serving as binder has been inserted between the two parts. To this end carriers consisting of nitrocellulose have been coated with a preparation consisting of gelatine pretreated by allowing it to swell in small quantities of water, dissolving the swollen gelatine by adding glacial acetic acid and diluting the gelatine solution with alcohol, acetone or the like.

In the case of cellulose acetate films a preparation has been applied containing, besides gelatine, acetic acid and alcohol, also small quantities of nitrocellulose, however the adhesive properties of a sensitive layer fixed to the film `by means of this preparation have frequently been found to be unsatisfactory, since the physical properties of the cellulose acetate vary from batch to batch.

In the case of films prepared from certain kinds of diacetates and more especially triacetates and mixed cellulose acetate esters the preparations described above are an absolute failure, for, while the gelatine or emulsion may adhere firmly to the intermediate layer formed of such preparation, the cohesion between the intermediate layer itself and the film body is not a satisfactory one.

I have now found that a perfect adhesion can be attained provided that the solution from which the intermediate or binding layer is produced, contains as a constituent a certain proportion of the material constituting the film body, l. e.

the same or a similar cellulose derivative, or some of the cotton product used in the preparation of the body material.

While it appears impossible, at the present time, to account with any degree of certainty for the increase in the adhesive power, which is thus attained, an explanation which appears to offer itself by way of suggestion, is that the more or less finely dispersed gelatine particles, when drying, are cemented to the film body by the drying cellulose ester admixed to the gelatine. Probably cellulose compounds of a different type, such as the nitrocellulose previously suggested as a constituent of such intermediate layer, are not capable of adhering to the surface of the cellulose ester film body as firmly as a layer containing the same ester or the cotton, from which it is prepared.

By adding to the intermediate layer some of the fllm body material, I obtain the further advantage that the quantity of solvents liable to attack the lm body material and to cause warping of the lm, can be reduced considerably. I am further enabled to dispense with the addition of stronger acids such as the acetic acid, which is very desirable from a photographic standpoint, for, when the intermediate layer dries down, the acetic acid present therein will not evaporate altogether and the traces of acid remaining over in the emulsion will cause a reduction of the storing capacity and the resistance against the influence of higher temperatures (in hot climates), the emulsion being liable to become foggy and less sensitive to light.

In the accompanying drawing I have, without restricting my invention thereto, shown by way of example a lm embodying my invention, the view being a conventional exaggerated crosssectional showing.

In practicing my invention, I may for instance proceed as follows:

I allow 10 parts by weight gelatine to swell in 30 parts water, in which 5 parts salicylic acid are dissolved, and I then add a solution of 10 parts of the film body material such as for instance cellulose triacetate in 800 parts acetone, 1000 parts ethanol and 1200 parts methylene chloride.

'I'his solution is poured for instance on a cellulose triacetate film containing tricresyl phosphate and other softening agents. After thev solvents have been evaporated, the emulsion is poured on the intermediate layer thus formed.

'Ihe percentage of filmmaterial or cotton to be dissolved in the solution designed to form the intermediate layer depends from the physical and chemical properties of the body material and the character and thickness of the hydrophil colloid v layer (for instance the photographic emulsion) to be subsequently deposited on the intermediate layer. `VYIt may vary for instance between onetenth oi.' and three times the quantity of gelatine incorporated in the intermediate layer.

This layer has been found to nrmly cement the emulsion to the nlm body.

I have found that I may obtain a similar en'ect. when incorporating in the solution forming the intermediate layer a cellulose compound or cotton oi the same type, however possessing physical properties diil'ering from those of the nlm body material. For instance in the case ot a nlm formed from highly viscous cellulose triacetate, I may use an intermediate layer containing a low viscosity triacetate or a mixture thereof with the same high viscosity material.

Obviously my invention is not limited to intermediate layers formed with gelatine, but is applicable also to layers containing any other kind o! colloids of similar action, including agar-agar, isinglass, albumen etc.

Of the hydrophil colloids which may be spread on the intermediate layer. I may mention, besides gelatine and photographic emulsion. also agaragar, albumen, gum arabic etc. and mixtures ot two or more of these substances.

It is however not necessary that the colloids contained in the intermediate layer and the superposed layer (sensitive layer) be identical, and I may for instance pour an agar-agar solution on an intermediate layer formed with gelatine.

Various changes may be made in the details disclosed in the foregoing specincation without departing from the invention or sacrincing the advantages thereof.

I claimzl l. Photographic nlm comprising in combination, a nlm body containing a cellulose' ester, a

said nlm body and said sensitized layer and being a substantially homogeneous mixture oi! a hydrophil colloid and a cellulose ester of the same chemical composition as the said cellulose ester contained in said nlm body.

2. Photographic nlm comprising in combination, a nlm body containing a cellulose ester, a sensitized layer and an intermediate substratum layer inserted between said nlm body and said sensitized layer and being a substantially homogeneous mixture oi a hydrophil colloid and the same cellulose ester as said nlm and which is ilterunited with said nlm and with said sensitized yer.

3. Photographic nlm comprising in combination, a cellulose acetate nlm body, an intermediate substratum layer on said nlm body being a substantially homogeneous mixture o! cellulose acetate and a hydrophil colloid, and a sensitized layer on said intermediate layer, the said substratum layer being inter-united with said nlm body and with said sensitized layer.

4. Photographic nlm comprising in combination, a nlm body containing a cellulose ester. a sensitized layer and an intermediate substratum layer inserted between said nlm body and said sensitized layer and being a substantially homogeneous mixture of a hydrophil colloid and from one-tenth to the treble, calculated on this colloid. of a cellulose ester containing the same acid radical as said cellulose ester contained in said nlm body.

5. Photographic nlm comprising in combination. a nlm body containing a mixed cellulose acetate ester, a sensitized layer, and an intermediate substratum layer inserted between. and inter-united with. said nlm body and said sensitized layer and being a substantially homogeneous mixture o! a hydrophil colloid and a cellulose esterofthesameacidasthenlmbody.

WAL'I'HER PORSTMANN. 

